Treatment of poly-unsaturated fatty acids



TREATMENT OF POLY-UNSATURATED FATTY ACIDS I William s. Baldwin, St. Paul, Don E. Floyd, Robbinsdale, and Raymond F. Paschke, Anoka, Minn., assignors to General Mills, Inc.,a corporation of Delaware No Drawing. Application May 7,1956

. Serial No. 582,933

3 Claims. (Cl. 260-413) The present invention relates to the treatment offun saturated fatty acids at elevated 'te'rnperatures in the presence of certain hydrogen transfer'catalysts, whereby the unsaturated fatty acids change to forms which have much lower iodine numbers than the original materials. During the treatment two major changes are involved: (1) intramolecular..cyclization within the unsaturated fatty acid chain through additions involving one or more double bonds; (2) aromatization of the cyclized molecules to give carboxylic acids containing'aroniatic rings. Hy drogen released during the aromatization may be released as such, or may reduce double bonds present in the unsaturated material. v g

This application is a continuation-in-part of our earlier filed application entitled Treatment of Unsaturated Fatty Acids, Serial Number 275,246, filed,March 6, 1952, and now abandoned. 7 f

It is an object of the present invention to provide 'a novel process of treating poly-unsaturated fattyacids at elevated temperatures in the presence of certain hydrogen transfer catalysts to effect a reduction in the iodine nur'n ber of the material. 1 v

' It 'is'another object of the present inventionto providethe novel product produced by the" process herein "described.

The invention is applicableprimarily with'linoleic acid compounds, i} 'e., pure linoleic acid, its esters, complex mixtures of fatty iacidscontaining a preponderance "of poly-unsaturated acids v.and '1yiariouscommon derivatives of linoleic acidsuch as ..it's nitriles and amines. These compounds or mixtures are best characterized byrefer; ence to their iodine number, which is the numberfiof 236,815 Patented Jan. 13, 1959 the aromatization may reduce the monounsaturated mabe obtained' Forpexample, 50 g. of the methyl esters of salflower oilfatty acids heated for 4 hours at 180 C. in the presence of,3. g. of 10% palladium-on-charcoal catalyst showed formation of 18% of conjugated diene unsaturation; infraredganalysisshowed the presence of both conjugated and unconjugated trans double bonds.

The reaction may be conducted at atmospheric pressure, under reduced pressureyor atsuperatmospheric pressure: It is desirable, although not absolutely necessary, to blanket the mass with inert gas when heated'at atmospheric pressure o rfat sup eratmospheric pressure.

It will be. recognizedthat-various active noble-metal hydrogen transfer catalystsmay be employed in accordance with the teachings of this invention. By the-use of i this class of/catalysts it is possible to obtain high yields of a characteristic and strong infrared adsorption band in is derived'frorn a C1 fattyacid ester. w

grams of halogenexpressed as iodine absorbedi'by 'a' 100 gram sample. vjForjthe purpose of this invention, these mixtures should have" an iodine num ber of "at least 130 and preferably-150. Of course, linolenic; acidor'more highly'runsaturated fatty acids are other naturally occurring with the teachings, this'ifivention'. Howeven'as 'a practical matter the-primary source of poly-unsaturated monocarboxylic acids containing 18 carbon-atoms having sufficient-unsaturation 'forthe purposes of this invention will be linoleic acidcompounds. A ready source of linoleic acid' are naturally occurring oi-ls which' have a relatively high iodine number; Illustrative oils are soybean 'oil, safiiower oil, peanutoih-sunfloweroils, fish oils etc.

Where poly-unsaturated fatty acids are employed alone, as for example, linoleic acidgthe reaction results in intramolecular cyclization, of th'e'fatty acid chain, followed the aromatization of the cyclized molecule. Hydrogen released during the aromatization may reduce "double 25% and above ofathe aromatized acids which contain the 133p region. L Illustrative catalysts are palladium, palladium salts, platinum oxides and platinum. Because these 7 catalysts are expensive their use can be extended by using them on'various relative inexpensive carriers. Illustrative inexpensive carriers are carbon, activated carbon, chromium oxide, molybdenum oxide and alumina.

I The time period will depend upon the temperature and the, amount of catalyst employed. Usuallylhe reaction is carried out untilan iodine number. of aQ- or less is The aromatizati n products produced by this invention are'illustrated by the following structural formula, "which if remnan @(onmooon' I in which the sum of x andy in any one molecule is equal to 10 and y is atleast Sand lessthan S and Ris hydrogen or a lower alkyl radical containing less than 4 carbon atoms. As this structure hasbeenunequivocally e stab f poly-unsaturatedacids which may be used in; accordance Y; fished it fully pl i unexpected p in iodine value of -themate'rial's,whibhfare"treated in accordance with the-present teachings. For-although the resulting ortho-substituted aromatized acids have 3 double bonds in their aromatic nucleus none of 'these double bonds will absorb halogen-under the conditionsemployed in the analytical determination of an iodineinumb era .Likewise, it willbe seen that linoleic acidmust'give up two molecules "of hydrogen in the formation of'the above aromatic acid.

with 15 is at a? wa ichl I 3 10% palladium on charcoal catalyst and 300g. of a mixture of fatty acids derived by the fractional distillation of tall oil, the mixture containing 44.2% linoleic acid, 7% saturated acids, 1.3% rosin,,2; 4%-of unsaponifiable material, and 45.1% (by dilferencelof oleic acid. The autoclave was flushed with nitrogen and sealed. The contents were "heated to 270 C. and held 'at'that temperature for 6 hours. The reaction mixture was-cooled and diluted with 400 ml. of a petroleum solvent (Skellysolve C). The catalyst was filteredolf'and the solvent distilled from the filtrate. The efiect of the treatment on linoleic acid content and iodine number is as follows:

Original Reaction Fatty Product Acids Linoleic acid content, percent 44. 2 Iodine number 1.25. 30. 7

A portion of the product was distilled under'reduced pressure in an alembic still, which left a residue of 4.5% indicating that the extent of polymerization during the reaction was relatively slight. I

182.3 grams of the distillate from the reaction product were esterified as follows: 1400 ml. of methanol and ml. of concentrated sulfuric acid were added and the reaction mixture heated under reflux in the-usual manner. There was obtained 165 g. of esterified material. 140 grams of this material were subjected to fractional distillation using a Podbielniak Hyper-Cal column at a head pressure of 4.5-5 mm. and a reflux ratio of 10 to 1.

Fractions 1 to were collected and analyzed. Thev fractions were selected as-much as possible at constant boillng levels. The-results obtained are shown in the following table:

Fraction No. Weight, B. P., Iodin Saponifim,

g. G./5 mm .No. cationNo.

114-131 70. 8 1. 4453 131-125 72: 7 p 3. 2 1. 4380 125-186 61. 5 4.0 1. 4350 136-140 37. 0 2. 0- 1. 4353 140-164 19. 3 118. 1 1. 4440 164-170 13. 5 186. 0 1. 4390 170-181 45. 3 167. 5 1. 4550 181-187 42. 4 176. 8 1. 4510 187-186 29. 7 186. 1 1. 4482 187-187 25. 3 188. 4 1. 4470 187-188 21. 9 189. 4 1. 4472 188-186 19. 3 190. 2 l. 4467 186-183 17. 1 190. 5 1. 4471 183-146 Y 13. 9 189. 5 1. 4490 Pot residue; not enough to push through column.

Fraction 15 was saved using an alembic still, as

Weight, B. P., Iodin Saponifinn g. O./.03 mm. No. cationNo.

Distillate from pot residue 20. 2 127-134 25. 7 176. 8 1. 4771 The preceding table shows that the first four fractions totaling about 18% consisted largely of low-boiling unsaponifiable material. Fraction 5 was an intermediate fraction, while fraction 6 consisted largely of methyl palmitate. Fractions 7and '8 were intermediate fractions containing methyl palmitate, methyl oleate, and unsaponifiables. Fractions 9 to 14 werecomposed of mixtures of methyl oleate and methyl stearate with the ratio of stearate to oleate increasing in the later fractions. Fraction 14 also contained a little of the material later found concentrated in fraction 15. This is indicated by the refractive index. The oleate and stearate-mixtures accounted for about 43.5% of the totaL.

The final fraction (No. 15) amounted to 15-16% of the total and had very unusual properties4-a combinaj- 9.8 g. of concentrate.

tion of low iodine number, very high refractive index, and a boiling point just higher than methyl stearate, indicating the presence of aromatic constituents. Since aromatic or cyclic compounds do not form adducts with urea, while straight chain aliphatic compounds do, this fraction was treated with urea (in methyl isobutyl ketone solvent). The filtrate material, containing products which did not form adducts with urea,'was recovered. From 12.96 g. of fraction 15 distillate there was obtained A portion (5.9 g.) of this concentrate was saponified by boiling with alcoholic potassium hydroxide, and the unsaponifiable material (amounting to 0.65 g.) was removed by extracting the diluted soap solution with ether. The soaps were acidulated to give 4.7 g. of purified acids. These acids re-esterified with 40 g. of methanol in the presence of 1 drop of concentrated, sulfuric acid. The isolated liquid methyl esters from the esterification weighed 4.4 g. and had the following characteristics:

Evidence for presence of an Infrared analyses r aromatic ring.

7 Example 11 Methyl linoleate having a refractive index of and an iodine number of 170.5 was prepared from safflower oil.

200 g. of this methyl 'linoleate was heated at 270:5 for 6 hours in the presence of 10 g. of palladium on charcoal. The palladium on charcoal catalyst was 10% by weight palladium. This treatment resulted in a reaction mixture having a refractive index of nD =1.4625 and an iodine number of 43.9.

The reaction mixture of esters after being washed with methanol and hexane and filtered totalled 170 g. of a clear, light-colored ester. This purified mixture was then separated into 'two fractions with urea. The urea adduct fraction totalled 68 g. of a mono-olefinic ester and 31.6 g. methyl stearate. The non-adduct fraction had a refractive index of n =1.4868' and contained 46 g. monomeric aromatized'fattyacids and 11.9 g. of a polymeric product.

The 46 gm. fraction of aromatized monomeric acid had an I. -V. of 3.2 and asaponification number of 192.7. This fraction was purified further by. distillation in a Podbielniak miniatureHypercal column at 15 mm. pressure. Of'the 20 fractions collected, fractions 2 to 16 had similar infrared spectra. The characteristic portion of these spectra was that they all had a strong band in the region of 13.3;1.

Fraction 13 from the Podbielniak distillation was oxidized t0 phthalic acid with KM O Phthalic acid was definitely identified by crystallization from carbon tetrachloride and a mixed melting point with known phthalic acid taken. The melting point of pure phthalic acid is 131.0-131.6 and the mixture melted at 130.0-1308 which is conclusive .of the presence of phthalic acid.v This was confirmed by the preparation of phthalimide by heating the oxidized-products from above with concentrated NH OH which resulted in a compound having a melting point of 225230 C. A

tion may be used in the same applications as other monocarboxylic acids and their derivatives. Illustrative uses in which they may be employed are in the plasticizing of vinyl compounds such as polyvinyl chloride, as an oil additive to improve its viscosity index, and as surface active agents such as soaps. The aromatized acids have lower melting points than ordinary fatty acids which will permit their use in many applications in which ordinary fatty acids are unsuitable. Furthermore, the aromatic ring undergoes the typical reactions of aromatic compounds, e. g., nitration, diazotization, sulfonation, halogenation etc.

Now, therefore, we claim:

1. Process of aromatizing a linoleic acid compound which comprises heating a compound selected from the group consisting of linoleic acid and its esters to about 270 C. in the presence of a noble metal active hydrogen transfer catalyst to produce amixture of aromatic orthosubstituted di-alkyl monocarboxylic acids which are characterized by having a strong infrared adsorption band in the 13.3,1i region.

2. Process of aromatizing a polyunsaturated higher fatty acid compound which comprises heating a compound selected from the group consisting of polyunsat- 5 nrated higher fatty acid and its esters to about 270 C. in the presence of a noble metal active hydrogen transfer catalyst to produce a mixture of aromatic orthosubstituted di-alkyl monocarboxylic acids which are characterized by having a strong infrared adsorption band in the 13.3;i region.

3. A method of aromatizing poly-unsaturated acids which comprises heating naturally occurring aliphatic carboxylic acids and their esters having an iodine number greater than 130 and containing 18 carbon atoms in the presence of a noble metal active hydrogen transfer catalyst to produce a mixture of mono-carboxylic acids having an iodine value of less than 50 and in which at least percent of said acids contain an aromatic nucleus and have a strong infrared adsorption band in the 13.3,u region.

References Cited in the file of this patent FOREIGN PATENTS 

1. PROCESS OF AROMATIZING A LINOLEIC ACID COMPOUND WHICH COMPRISES HEATING A COMPOUND SELECTED FROM THE GROUP CONSISTING OF LINOLEIC ACID AND ITS ESTERS TO ABOUT 270* C. IN THE PRESENCE OF A NOBLE METAL ACTIVE HYDROGEN TRANSFER CATALYST TO PRODUCE A MIXTURE OF AROMATIC ORTHOSUBSTITUTED DI-ALKYL MONOCARBOXYLIC ACIDS WHICH ARE CHARACTERIZED BY HAVING A STRONG INFRARED ADSORPTION BAND IN THE 13.3U REGION. 